The invention relates to an adjustable filter regulator for a microspectrophotometer, providing an adjustment knob coupled with a scale. The adjustment of the regulator enables the interference filter to be set for the particular wavelength to be filtered.
Microspectrophotometric reflection measurements are preferred in mineralogy, petrography, metallography, etc., when dealing with defined wavelengths. Transmission measurements often even take place in routine fashion involving two wavelengths which are always constant (for instance, in conjunction with the two wavelength method according to Arnstein and Patau).
Graduated interference filters are, to be sure, relatively inexpensive. However, they have the disadvantage that their graduation is not linear, that is, equal displacement length of travel do not correspond to a proportional wavelength change. Hence, solution of the present problem must start from the principle that the wavelength scale, in the use of graduated interference filters, is not linear. In addition, specimen dispersions dependent on the vaporization of the filters occur, which means that for every photometer or interference filter, a separately prepared individual scale is required. In reference thereto, what has always been done heretofore is, that the interference filters were carefully set by hand to the given value wanted. This hand-setting naturally leaves much to be desired as regards accuracy. Moreover, it requires an appreciably long time to make this hand-setting. However, it is especially disadvantageous in these hard-set devices that it is not possible to rapidly set and reliably reproducible preselected values when required, that is, during the measurement.